The foregoing abstract is not to be taken as limiting the invention of this application and in order to understand the full nature and extent of the technical disclosure of this application reference must be made to the accompanying drawings and the following detailed description.
The invention pertains to a retreaded belted tire and a method of preparing same. It is particularly suited to retreading a heavy-service radial carcass tire of the type having a belt structure including a plurality of cord-reinforced belts the radially outermost of which is substantially narrower than that lying immediately radially inward thereof. These belts cords are typically of wire, aramid, fiberglass or other high modulus material.
Many heavy service radial carcass tires today, such as those used on heavy duty highway trucks (for example, semi-tractors and their trailers) have a belt structure overlying the carcass including three or more layers of belts of varying widths. The radially outermost layer of the belts used in many tire designs is considerably narrower than that of the belt layer lying immediately radially inward thereof. As used herein, "radially outermost" means that which is farthest away from the axis of rotation of the tire. Present retreading methods employ a crown preparation technique for removal of a portion of the existing crown area rubber material which allows substantial quantities, for example, up to 3/16 to 1/4 inch in thickness, of the existing rubber material lying radially outwardly of the belt structure to remain on the prepared tire. During previous service of the tire casing this rubber material has been subjected to substantial mechanical action and temperatures above ambient, particularly at the edges of the belt structure. When a new tread is placed over a heavy layer of original rubber material service life of the retreaded tire may be reduced either due to tread separation or separation at the edges of one of the two most radially outward belts. As used herein "radially outward" and related forms means directed away from the axis of rotation of the tire.
It is an object of this invention to provide a method whereby the amount of existing rubber material lying radially outwardly of the belt structure is minimized in the retreaded tire to improve service life of the retreaded tire.
It is another object of the invention to provide a method for retreading a radial carcass belted tire of the type which has its radially outermost belt layer of a width substantially less than that of the belt layer lying immediately radially inward thereof so as to leave not more than 1/8 inch of existing rubber material lying radially outwardly of the edges of the radially outermost two belt layers.
It is still another object of the invention to provide a retreaded radial carcass tire having a dual radius crown area transverse profile, the radius of transverse curvature of the center portion being greater than the radius of transverse curvature of either shoulder portion.
It is a further object of the invention to provide a mold for use in bonding newly added unvulcanized rubber material to a tire prepared for retreading according to the invention, the mold having a radius of curvature complementing that of the tire prepared according to the rubber removal method of the invention.
These and other objects and advantages of the invention will become apparent as the description proceeds.